The invention relates to a turbo supercharging system for delivering a charge to an internal-combustion engine, having plural controllable charge air compressors always in a driving connection with an internal-combustion engine exhaust gas turbine during the operating periods of the internal-combustion engine and wherein switching means are provided for the plural charge air compressors to control inlet pressure led to the plural charge air compressors.
In the partial load and partial rotational speed operation of a supercharged internal-combustion engine, it is advantageous to adapt the turbo supercharging system to reduce development of engine exhaust gas energy while optimizing the charge air supply for the engine.
A supercharging aggregate of this general type is known from German Patent Document DE-PA 39 32 721 wherein the charge air supply of the internal-combustion engine takes place by connecting and disconnecting one of two parallel operating charge air compressors in accordance with engine operating conditions.
Although the driven charge air compressor, which is to be disconnected, is connected to a common air intake line, it is set to a so-called idle delivery by opening of a venting outlet. At the rotational rotor runner speed of the supercharging system determined by the exhaust gas turbine and by the other charge air compressor which is set for delivery, the idle-delivery charge air compressor has a power consumption rate which is significantly reduced in comparison to its designed operating point. The low pressure ratio obtained stems only from flow and separation losses while the air mass flow stems from the momentary rotational speed of the rotor runner. Nevertheless, the power consumption of the idle-delivery charge air compressor is of an amount which noticeably impairs the efficiency of the supercharging aggregate.
It is therefore an object of the invention to achieve a minimizing of the power consumption of the charge air compressor set to idle-delivery for a turbo supercharging system with controllable charge air compressors always in a driving connection with a driving motor.
According to the invention this object is achieved by having a distributing means located upstream of a charge intake of each controllable charge air compressor which can be switched in several steps to control the origin of a source of charge to each of the plural compressors; wherein a flow control means is arranged between the distributing means and the charge intakes for controlling the charge flow at the charge intakes; wherein at least one gas supply line is connected to the inlet of each distributing means; and wherein a source of air is also connected to said inlet of said distributing means.
It is advantageous if the gas supply line is connectable by the distributing means to an inlet of one of the charge air compressors supplying charge to the internal-combustion engine to supply air to said one compressor from another of said compressors. The gas supply line can be connected to an exhaust plenum line of the internal-combustion engine to permit the distributing means to provide internal-combustion engine exhaust to the inlet of one of the plural compressors or to an exhaust pipe of the exhaust gas turbine. It is desirable if a reverse-flow blocking device is arranged in the exhaust pipe downstream of a connecting point for the gas supply line and if a gas cooler is inserted into the gas supply line between the exhaust pipe and the distributing means.
It is also advantageous if an exhaust gas compressor is located downstream of an exhaust gas cooler located in the gas supply line to draw air therethrough.
As an alternative there can be two gas supply lines with the gas supply line connected to the exhaust pipe being connected to a gas supply line from an outlet of one of the plural compressors and these combined two gas lines connected to the distributing means. Here an can be provided downstream of the connection of the two gas supply lines and upstream of the distributing means. One can also have an exhaust gas compressor connected to the gas supply line downstream of the connection of the two gas supply lines. Also, one can provide a switchable blocking means between the exhaust gas compressor and the connection of the two gas supply lines.
The advantages achieved by the invention are that separation losses because of a faulty flow onto the rotor runner of the compressor, occurring during the idle delivery of a charge air compressor, can be eliminated by influencing the air flow at the compressor rotor intake; that a power consumption of the idle-delivery charge air compressor that approaches zero can be achieved; that an increase of power delivery is achieved by gas removal at the outlet of the exhaust gas turbine; that the remaining existing power consumption of the charge air compressor, which has an idle delivery during the idling operation of the internal-combustion engine, is approximately compensated; that a mechanical uncoupling between the charge air compressor and its driving machine is not necessary; and that a rapid operational readiness is obtained in the case of a transition to the series connected condition of the charge air compressors.